This invention relates to molybdenum oxide briquettes. In one aspect, the invention relates to briquettes comprising molybdenum oxide (also known as "moly oxide") and a binder and in one embodiment, an inert filler, while in another aspect, the invention relates to molybdenum oxide briquettes in which the binder is an alkali metal hydroxide such as sodium hydroxide (NaOH) in combination with an inert filler such as a silica (e.g. a diatomaceous earth) or an alumina (e.g. an activated or fused alumina). In yet another aspect, the invention relates to a process for making a briquette comprising molybdenum oxide and a binder, optionally with an inert filler.
Molybdenum is a well known and extensively used alloying agent for producing stainless and other speciality steels. However, molybdenum is not found in nature as a free element and as such, it must be separated from the other elements with which it is associated in its natural state before it is useful as an alloying agent. Conventionally, this is accomplished by subjecting the molybdenum-containing ore to a series of beneficiation steps to produce molybdenite (MoS.sub.2) which is then converted to molybdenum oxide, i.e. a material containing mostly molybdenum trioxide (MoO.sub.3) with minor amounts of molybdenum dioxide (MoO.sub.2), molybdenum sesquioxide (Mo.sub.2 O.sub.3), other oxides of molybdenum, the oxides of other elements such as copper, iron, arsenic, etc., and gangue material (the latter two of which were either present in the molybdenum-containing ore or were acquired during the beneficiation process). The moly oxide is then typically compacted into a briquette which is suitable for use as an alloying agent, e.g. as a feed to a metallurgical melt in which it is converted to metallic molybdenum.
Briquettes are a preferred form of moly oxide for various reasons not the least of which is ease of handling and minimized dusting, the latter of which is not only hygienically and environmentally undesirable but also represents a potential loss of material. The conventional process for making moly oxide briquettes is well known, and it comprises blending in any conventional manner moly oxide with a binding material (comprising either a binder alone or a binder in combination with one or more other substances, e.g. fillers) to form a substantially uniform mixture which is then fed to any standard briquetting apparatus. The briquettes as produced by the apparatus are uncured (i.e. "green"), but they are typically cured (either under atmospheric or oven conditions) to some extent before packaging and shipment to a customer.
Important physical properties of a briquette are its resistance to breakage and dusting. From almost the moment a briquette is formed, it is subjected to both crushing and abrasive forces from contact with the briquetting equipment; curing, storing and packaging equipment; packaging material and, of course, other briquettes.
The resistance of a briquette to breakage and dusting is a function of many factors not the least of which is the nature and amount of binding material used to make the briquette. The binding material is selected not only for its ability to form and hold the moly oxide in a briquette shape, but also for its cost and ease of separation from the moly oxide in the metallurgical melt. Low cost is important because the binding material is sacrificial, i.e., it is not recovered for reuse, and ease and thoroughness of separation are important because binding material residue in most circumstances is considered an impurity in the steel.
Known binders include ammonium hydroxide solution, starches, gelatins, sugars, molasses, tall oil pitch and sodium silicates, and known fillers include wood flour, sulfur and phenolic resins in the form of microballoons. One important characteristic of an acceptable filler is the ability to readily vaporize under melt conditions.
While all of these binding materials are effective to one degree or another, none are completely satisfactory for any of various reasons. In particular, a continuing interest exists in identifying new binding materials that exhibit an ability to bind effectively into briquettes moly oxide of a very fine average particle size, e.g. less than 50 microns.